Process of cementing iron or steel.



Patented Nov. 26, I90]. C. DAVIS.

PROCESS OF CEMENTING IRON 0B STEEL.

(Application filed Sept. 27, 1901.) (No lllodel 3 Sheets-Sheet I.

. '17 z G I H M vexHo-L allbozmuzo Patented Nov. 26, mm.

' C. DAVIS.

PROCESS OF GEMENTING IRON 0R STEEL.

3 Sheets-Sheet 2.

(No Model.)

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No. 687,6l2. Patented Nov. 26, l90l.

C. DAVIS. PROCESS OF CEMENTING IRON UR STEEL. (Application filed se k.27, 1901.

(No Modem 3 Sheets8heet 3.

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19H; names PATENT OFFICE.

onELAND DAVIS, on THE UNITED STATES NAVY;

i aooizss OF CIIZIM'IENTING' IRON OR STE'EL.

sPEoIEIoATIoN forming part of Letters Patent No. 687,612, dated November2 6, 1901. Application filed September 27, 1901. Serial No. 76,765. (Nospeoimensi) To all whom it may concern.- 4BeitknownthatLCLELANDDAVIs,1ieutenant United States Navy, stationed atWVashington, in the District of Columbia, have invented certain new anduseful Improvements in Processes of Cementing Iron or Steel; and I dohereby declare the following to be a full, clear, and exact descriptionof the invention, such as will enable others skilled in the art to whichit appertains to make and use the 531116.

My invention relates to an improved method of cementing orsupercarbonizing steel or iron plates or Tails, ingots, or like articlesmade of iron or steel in which it is desired to obtain a hard surfacecapable of resisting the penetration of foreign bodies or of resistingwear.

My invention is particularly adapted to the manufacture of hard-facedarmor-plate; but it is also applicable to hardening the tread 'of railsof steel or iron or of hardening the face of other plates of steel oriron when desired.

In carrying out my invention I subject the face of the plate, eitherprogressively or the entire face at one time, to the action of heavyelectric currents passing either from carbon electrodes or through amass of carbon which may be in a granulated form. The face of the platewithin the path of the current is soon brought to a high heat and isimpregnated to a greater or less depth with particles of carbon carriedeither from the electrodes or from the mass of granular carbon placedover the face of the plate. The depth to which the carbon will becarried and the conse- 'quent hardening which will occur will vary withthe electric current and with the time that the treatment lasts. Whereit is desired to harden to a considerable depth below the surface, thetreatment may be prolonged; but where it is desired to harden only to aslight depth the treatment will be shorter. Sinceit would be ordinarilydifficult to secure current enough to treat the entire face of a largearmorplate at one time, it may be preferable to treat portions of theplate progressively, which may be done either by moving the electrodesover the plate or by.

moving the plate under the electrodes or by shifting the current fromone group of electrodes to another, in the meantime keeping the plateand the electrodes in the initial position. In the same Way, where railsor plates are to be treated the electrodes can be moved along the railor the rail moved under the electrodes, as may be preferred. Whereportions of the plate are treated progressively, the conductivity of themetal will ordinarily speedily produce the desired chilling effect, orthis may be supplemented by means of a spray of water or other chillingagent.

My invention will be understood by reference to the accompanyingdrawings, in which the same parts are indicated by the same lettersthroughout the several views.

Figure 1 is a diagrammatic view showing an armor-plate with electrodesarranged to treat the face of the plate progressively. The boxcontaining the electrodes is shown in section on the line 1 1 of Fig. 2.Fig. 2 isaplan view of a portion of the plate and of the box ofelectrodes shown in Fig. Fig. 3 is asectional elevation of a rail movingunder fixed electrodes. Fig. 4 is a sectional elevation of a plate andbox of electrodes, in which the plate and electrodes are mounted in thefixed position during the process. Fig. 5 is a plan View of a portion ofthe electrode-box shown in Fig. 4, the feed-wires being omitted. Fig. 6is a sectional elevation showing one means of automatically feedingelectrodes to the surface of the plate. Fig. 7 is a sectional elevationshowing the plate covered with a layer of granular carbon and beingtreated according to my invention, and Fig. 8 is an inverted plan viewof the movable covercontaining the electrodes shown in Fig. 7.

Referring now to Figs. 1 and 2, A represents the plate to be treated,which is mounted on suitable supports B, insulated, as at B. 0represents the electrodes, which are shown diagrammatically and whichshould preferably be arranged so as to feed automatically in thewell-known way-such, for instance, as shown in Fig. 6 of thedrawingswhere 0 represents a compound-wound solenoid. 0 represents ayielding attachment for the carbon electrode 0, and N and N are terminalconductors. N is a shunt-conductor by means of which the carbonelectrode is automatically kept at the desired distance so as to form anarc with the face of the plate A.

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This automatic feed is not a part of my present invention, and any othersuitable automatic feed may be adopted, if desired. These carbonelectrodes are mounted in a cover D on the box D, which is preferablyinsulated from the plate A, on which the box is moved. The box may bemoved by handles 01 or in any other convenient way. The electrodes arepreferably connected to the positive pole of the source of electricity,and the brokenofi fragments of carbon are carried down into the face ofthe plate, which speedily becomes highly heated locally on the surfaceand to a depth below the same. The 7 .rrent may be carried 0% throughany suitable contact E. The surface of the plate shown in Figs. 1 and 2is treated progressively, and when the carbon is introduced to thedesired depth the carburized portion may be hardened by sh utting offthe current, when the conductivity of the metal will speedily carry ofithe heat. The spray M is used during the carburizing operation toprevent annealing of the metal of the plate outside the box, and it maybe used after the operation on the carburized portion to assist in thechilling.

Referring now to Fig. 3, the box D carrying the electrodes, is securedon a suitable support Gr, and the rail F slides longitudinally throughthe box, the latter having approximately air-tight ends. The bottom ofthe box may be packed with asbestos (P, so as to keep the jointair-tight. The bottom of the rail f slides along over the rollers H. Thecurrent from the electrodes 0 enters the face of the rail f, whichspeedily becomes highly heated and impregnated with carbon, and thecurrent passing through the upper portion of the rail escapes throughthe contact E.

In both the above-mentioned forms of device any oxgen in the air in thebox containing the electrodes is speedily consumed, leaving inertnitrogen and other inert gases, and particles of carbon from theelectrode are carried into the body of the plate or rail being treated.

In the form of device shown in Fig. 4 the box D includes the entire faceof the plate and is packed with asbestos or like fireproof material, asat d. Carbon electrodes pass through the cover D of said boX, and thesolenoids C rest on the cap K, which is are automatically fed, so as tomaintain the electric arc, in any desired manner, such as that shown inFig. 6 and already described.

In the form of apparatus shown in Figs. 4 and 5 it would ordinarily bedifficult to keep all of the electrodes in operation at the same time,owingto the immense volume of current required, and therefore it wouldordinarily be desirable to operate the electrodes in groups, which maybe done by any suitable switch arrangement well known in the art, one ofwhich is shown in Fig. 7. In the form of device shown in Figs. 4 and 5the plate and the box for the electrodes remain in position until thecementation of the plate is completed,when the box D is removed and theplate is taken out and subjected to such subsequent treatment as may bedesired.

Instead of depending upon the carbon in the electrodes 0 to impregnatethe surface of the plate, as described with reference to Figs. 1 to 6,the carbon may be applied to the face of the plate in the powdered orgranulated form and the current passed from the electrodes through thiscarbon, as shown, for instance, in Fig. 7. In this case high heat wouldbe generated by imperfect contact of the electrodes and by theresistance offered by the powdered carbon. In this view the surface ofthe plate is preferably packed air-tight in the masonry P, having therefractory lining p, and the face of the plate is covered with a layerof powdered carbon 0, beneath the cover D This cover contains refractorymaterial R, in which the electrodes 0 are embedded. These electrodes maybe of carbon or other suitable conductor, and when the cover is inposition they rest on top of the layer of carbon 0. These electrodes maybe cut in or out in groups by switches 0 The bottom of the plate may bekept cool by air-currents through the twyers Q. When the curren isturned on the electrodes 0 the face of the plate speedily becomesintensely heated, and the particles of carbon are absorbed to a depthdepending upon the length of time that the current is continued. Whenthe treatment is completed, the cover may be removed in any convenientway, as by means of the cable T over the pulley S. All parts of the faceof the plate A may be treated simultaneously if current enough can besecured, or the parts of the face of the plate may be treatedprogressively, as by cutting in and out the switches 0 When the elec--trodes C are of carbon, the granular mass may be omitted, although Iprefer to inter pose a layer of powdered carbon.

' It will be seen that in all the instances hereinbefore mentioned theopposite side of the plate will be at a lower temperature than the sidebeing treated, and this difference in temperature may be furtherincreased, if desired, by artificial means, as by the twyers 1 shown inFig. 7. supported on the posts is. These electrodes It is well known inthe art that the affinity 5 of steel or iron for carbon increases withthe temperature until, when the metal is-molten, I carbon is rapidlydiffused throughout the entire mass. It will be seen that by thehereindescribed method of treating steel or iron the face may be broughtto any desired high temperature, even to the point of fusion, and thatthis high temperature may be carried to any desired depth below thesurface, being limited only by the necessity of keeping the back of theplate cool enough to maintain the shape of the plate. Thus it will beseen that carbon can be introduced to any desired depth below thesurface of the plate. Moreover, by

having the face of the plate fused to a prescribed depth, as may be donewith the apparatus herein described, the carbon may be uniformlydiffused through the molten part of the plate and will then shade offdecrementally as the depth below the molten portion increases. Moreover,at the same time the process of cementation is effected rapidly andcompletely. Again, it is possible to treat the face of the plateprogressively a portion at a time without the expensive apparatusordinarily required for this purpose and without liability to thecracking and warping that result from the tedious process now in use.

In the form of device shown in Fig. 7 it is essential that the face ofthe plate and the layer of carbon above the same be screened from theatmosphere. In the form of device shown in Figs. 1 to 5 it is preferablethat the face of the plate and the carbon electrodes be screened fromthe air; but this screening is essential only when the surface of theplate is to be heated to a very high temperature.

It will be obvious that various modifications might be made in theapparatus for carrying out the herein-described process, and I do notmean to limit my invention to any particular apparatus for the purposestated; but What I claim is'- 1. The process of carburizing steel oriron plate, which consists in intensely heating one face of the plate bymeans of an electric current passing through that face of the plate froma carbon conductor, and during the operation screening the conductor andthe part 3 5 of the plate under treatment from the air, substantially asdescribed.

2. The process of carburizing steel or iron plate, which consists inintensely heating one side of the plate by means of an electric our 40rent passing through that face of the plate from a carbon conductor, andduring the op eration screening the conductor and the part of the plateunder treatment from air, and simultaneously maintaining at a lowertemperature the opposite side of the plate, substantially as described.

3. The method of cementing steel or iron plate which consists inmaintaining for a limited time an electric are between a carbon 56electrode and the face of the plate, and simul taneously screening thesaid electrode and that part of the plate to be treated from theatmosphere, substantially as described.

In testimony whereof I affix my signature in presence of two witnesses.

OLELAND DAVIS.

Witnesses:

J STEPHEN GIUSTA, JANE LEE HART.

